Some examples have been already known for a production method for selectively producing an asymmetric 2,3,3′,4′-biphenyltetracarboxylic acid tetraester (hereafter, it may be abbreviated as a-BPTT) by oxidative coupling a phthalic acid ester by using a catalyst comprising palladium in the presence of a molecular oxygen.
For example, the patent document 1 discloses a production method for producing a-BPTT by oxidative coupling a phthalic acid ester in the presence of an organic palladium salt and an organic copper salt in a reaction liquid under an atmosphere containing a molecular oxygen. Specifically in example 16, 20.4 g of a-BPTT is obtained from the use amount 3.0 mmol of bis(acetylacetonate) palladium chelate salt by a reaction for 7 hours at 140° C. Here, in terms of a turnover number of catalyst (hereafter, it may be abbreviated as TON) represented by {product (mole number)/catalyst palladium (mole number)} for the generation of a-BPTT, the TON of palladium in this method was very low, i.e. about 18, and a considerable amount of valuable noble metal of palladium is consumed. Therefore, this method is economically disadvantageous.
The patent document 2 discloses a method for producing a-BPTT, comprising oxidatively coupling a phthalic acid ester using a palladium salt and a copper salt at a high temperature under an atmosphere in the presence of a molecular oxygen while continuously or intermittently supplementing a (3-ketone into a reaction system.
Here, example 1 discloses that the TON regarding the generation of a-BPTT was improved up to about 129; however, the use efficiency of valuable noble metal, palladium was not sufficient, and there was room for further improvements.
In terms of the supplementation of β-diketone in this production method, it is described that preferred is a method of feeding about 1.0 to four-fold moles relative to palladium salt in onset of reaction and then supplementing one to ten times intermittently with a ratio as mentioned above in every about 0.5 to 4 hours passing; or a method continuously supplementing it in a ratio of about 0.5 to three-fold moles per hour relative to palladium salt immediately after the beginning of reaction. However, the manner of supplying β-diketone specifically shown in the example was merely a process of feeding it (as an initial feeding) together with palladium salt in onset of reaction, and subsequently, while heating and reacting at an elevated temperature, supplementing it at 2 hour intervals.
In addition, it is merely explained that the β-diketone in this production method may be those capable of forming a palladium chelate salt. Those shown in the specific examples were only acetylacetone.
The non-patent document 1 investigated the effect of substituent groups on the ratio of enol form in a keto-enol equilibrium of β-diketones; however, it does not mention a role of the β-diketones as a catalytic component.